I'm not sure it's doing it right for me, it sounded very quite. Like, my fridge??? I got 1.2V. But seems wrong. Even with 12db of headroom, it was much less than the average loudness of the music. Thoughts?

220 Hz : 2.02 V on the midbass, 0.13 V on the woofers
120 Hz : 1,77 V on the midbass, 0.87 V on the woofers

120 Hz sits at the cross over, grossly at -6dB on each output, so it's the 220 Hz that has to be retained.

The room core is 9 x 12 x 5 (meters). Listening distance is 7 meters, mids efficiency must be around 96dB. Drivers for both channels are 8x15" for the woofers and 10x12" for the mids, so the acoustical level can be considered as louder than the relaxed listening. The tones themselves were very loud, at the limit of being a nuisance.

Great, thanks. So I'll count you as basically 2V, as that's the highest level you found.
Those of you with active crossovers will find this test a bit more difficult as you can't just measure at "the amp". You have to measure each section. But I hope that it teaches you something about your levels.

I can supply tones at other frequencies, if needed. Above about 400Hz I don't know how accurate volt meters are. Some will be, some won't be. Lower tones are not a problem.

For those who own an oscilloscope, you can set your volume to loud and look for the peak voltages on music. Once you find the peaks, just divide by 4 to arrive at the -12dB of the test.

I've voted "2 or less".
I very rarely listen so loud. usually more less (big green smile were here. For some reason (???)emoticons not work in my posts.. "Disable smilies in text" is Off).
p.s.: woofers are equalised about +13dB @ 30Hz. so there is more voltage..

AV receiver did *not* like the additional capacitive load when I ran the meter in parallel with my 4-ohm speakers and went into some sort of oscillation feedback. Had to make all measurements with the speakers disconnected, just driving the meter.

I am also not sure if the "sample music" I listened to was normalized to the same level as the tones. I tried to pick music with a fair amount of dynamic range. All MP3s were played through my Tivo from my home music server.

Speakers - DIY 2-ways with Vifa M18 (4 ohm) woofer and D27 tweeter. The LEAP printout show it about 89dB efficient at 220Hz, but I'm not sure if that is per watt or at 2.83VAC.

Room - Large and odd shaped. Roughly 24x28 feet with a 24 foot ceiling peak. 30% of that space has a loft over it. There is also a open kitchen area to one side with an additional 300 ft^2.

Speaker front baffles are placed about 18 inches out from the wall with about 8 ft. of separation. Listening position for "laid back and loud" was about 15 ft. Critical listening tends to be done from around 8 ft.